Diagnosis by chest X-ray may not detect pneumonia, particularly early in the course of pneumonia. High-resolution computed tomography scan (HRCT) may increase the ability to detect early pneumonia, and show how severe the course of pneumonia will be. If HRCT imaging can provide better information to predict the severity of pneumonia, then perhaps the intensity of therapy can be matched more closely to the disease severity. Numerous researchers have used mice to compare severity of pneumonia from different strains of microbes, and the body's response to pneumonia, but none have used CT scans to assess pneumonia in mice. Micro-computed tomography (micro CT) is specifically designed for lab animals to be similar to HRCT, and is available in the NIH Mouse Imaging Facility. The use of mice permits study of pneumonia at known times & doses, and the effects of genetic modifiers can be examined using the wide variety of genetically modified mice now available. CT methods pilot-tested in mice have the potential to be quickly translated to human use. <br><br>This study is being conducted as an initial radiology feasibility study and subsequent parts. The radiology feasibility study is complete: Groups of mice had CT scans in the NIH Mouse Imaging Facility, 24 hours after they received different doses of bacteria injected into their airways to cause pneumonia. These CT scans were scored by 2 independent radiologists. Statistical analysis indicated a good correlation of scores with the bacterial dose given. Furthermore the correlation between lung CT scores and other more invasive measures of lung injury, such as lung lavage protein concentrations and lung wet to dry weight ratios appeared equivalent. These lung scores also correlated with the mortality of the bacterial dose administered. Thus lung CT appeared sensitive to the severity of pneuomia in animals. <br><br>In aditional studies we have tested the ability of miro CT to predict survival in this same model. To date however, based both on radiographer interpretation as well as a computerized system, micro CT does predict survival in this model.